BIO 104 5/2/96

Chordates
     Review of Chordates:  see May 1 lecture notes
     3 Subphylum:
          1) Tunicata
          2) Cephalochordata
          3) Vertebrata
     Fish:
          1) There are three classes of fish:
               1. Aganatha
               2. Chondrichtyes
               3. Osteichthyes
     There are four classes of Tetrapods:
          1. Amphibia
          2. Reptilia
          3. Aves
          4. Mammalia

SEE HANDOUT ON THE PHYLUM CHORDATA FOR FURTHER REFERENCE

Figure 18.2 (7 classes of vertebrates)
Figure 18.16 (Time line of terrestrial vertebrate evolution)



Vertebrate Evolution:
     -Jawless ancestral fishes evolved about 550 MYA
     -Jaws (modification of the gill arches first developed about
          410 MYA.  See Figure 18.5
     -Sharks evolved about 390 MYA:  most likely from placoderm 
          ancestors
     -The earliest ray finned fishes appeared about 300 MYA and
          had strong body armor.
     -Ray finned fish were replaced by teleosts (swim bladder) 
          about 100 MYA
     -Land was invaded by vertebrates (lobe-finned fishes) about
          100 MYA.  See figure 18.4
     -Amphibians that first appeared about 300 MYA had fishlike 
          bodies, short stubby legs, and lungs.  See figures
          18.11 and 18.2
     -Reptiles first appeared about 300 MYA and were dominant
          during the Mesozoic Era.  See figure 18.3
     -Archaeopteryx, the earliest known bird, appeared about 150
          MYA, and had feathers, but a limited ability to fly.
          See figure 18.24
     -Mammals first appeared about 200 MYA.  Maximum diversity 
          occurred 15 million years ago.  See figure 18.5

Dr. Barstow went through the "Phylum Chordata" handout.  It 
would be in your best interest to get this handout off the web
and familiarize yourself with it.  

The evolution of an amniotic or waterproof egg enabled bird and
reptiles to permanently move onto land.
          -The egg has its own food source, oxygen, and other
          controlled element essential for development.
          -This marked a major evolutionary advancement.

What to get from this lecture:
     -get some idea of the time line of evolution (see page 355)
          -it is a series of major extinctions
     -know characteristics and evolutionary sequences of the 
          organisms